Alpha-olefins, especially those containing four to twenty carbon atoms, are important items of commerce. They are used as intermediates in the manufacture of detergents, as monomers (especially in linear low-density polyethylene), and as intermediates for many other types of products. Consequently, improved methods of making these compounds are desired. Especially desired, is a process capable of making a range of linear α-olefins such as 1-butene and 1-hexene?
Most commercially produced α-olefins are made by the oligomerization of ethylene, catalyzed by various types of compounds, see for instance B. Elvers, et al., Ed. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A13, VCH Verlagsgesellschaft mbH, Weinheim, 1989, p. 243–247 and 275–276, and B. Cornils, ET al., Ed., Applied Homogeneous Catalysis with Organometallic Compounds, A Comprehensive Handbook, and Vol. 1, VCH Verlagsgesellschaft mbH, Weinheim, 1996, p. 245–258. The major types of commercially used catalysts are alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid such as AlCl3. In all of these processes, significant amounts of branched internal olefins and diolefins are produced. As these are undesirable byproducts, catalysts and/or processes that more selectively dimerize and/or oligomerize olefins would be very valuable.
The present inventors have discovered a new genus of catalyst precursors which, when converted into active catalyst is highly selective for the dimerization and oligomerization of α-olefins.
For additional background, see WO 01/21586 and WO 00/50470.